Method and system for imposing pressure on a wellbore packer

ABSTRACT

This specification discloses a method and system for increasing the hydrostatic pressure of a packer liquid on the upper side of a wellbore packer. A manometer-type fluid piston is used to increase the hydrostatic pressure by a predetermined amount.

United States Patent Luther H. Wilkinson Dallas, Tex.

May 29, 1969 July 13, 1971 Mobil Oil Corporation inventor Appl. No.Filed Patented Assignee METHOD AND SYSTEM FOR IMPOSING PRESSURE ON AWELLBORE PACKER 10 Claims, 2 Drawing Figs.

Int. Cl E211) 33/12 Field of Search 166/244,

References Cited UNITED STATES PATENTS 7/1889 Conklin 103/165 12/1911Wigle 103/1UX 9/1927 McMahon 103/165 12/1961 Ten Brink 166/57 X 3/1964Carlberg et a1. 166/244 X 1/1968 Whipple 166/303 x Primary Examiner-JanA. Caivert An0meys-William J Scherback, Frederick E. Dumoulin,

.Wi11iam D. Jackson, Henry L. Ehrlich, Andrew L. Gaboriault and SidneyA. Johnson ABSTRACT: This specification discloses a method and systemfor increasing the hydrostatic pressure of a packer-liquid on the upperside of a wellbore packer. A manometer-type fluid piston .is used toincrease the hydrostatic pressure by a predetermined amount.

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METHOD AND SYSTEM FOR IMPOSING PRESSURE ON A WELLBORE PACKER BACKGROUNDOF THE INVENTION This invention is directed to a method and system forincreasing the hydrostatic pressures exerted by packer liquids. Morespecifically, this invention concerns the use of a manometer-type fluidpiston in a wellbore to increase the pressure exerted by a packer liquidon a packer set in a wellbore.

Packer liquids are used to impose a hydrostatic pressure on the upper orwellhead side ofa packer which has been set, for example, betweenproduction tubing and easing ofa wellbore. Packer liquid use isparticularly important when packers are set above high pressureformations. The hydrostatic pressure imposed by the packer liquid on theupper side of the packer opposes the formation pressure existing on thelower or formation side of the packer and thus aids in maintaining thepacker in place.

Drilling mud in use in the wellbore when the packer is set is often leftin the annulus above the packer to serve as a packer liquid. Theproperties of drilling muds are usually such that they are notcompletely satisfactory as packer liquids. For example, the muds may becorrosive, thus causing tubing and casing failure. Also weightingmaterials and other chemicals used in the drilling muds may segregatefrom the liquid carrier and settle to the lower portion of the well,thus interfering with the pulling of the packer and causing expensiveworkovers.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided a new and improved system which is adapted for theapplication of pressure on a well packer. The system is employed incombination with a well which is equipped with an outer conduit, such asconventional well casing, and an inner conduit, such as a tubing stringutilized for the the production of fluids from the well. The well isfurther equipped with a packer which is set in the annulus defined bythe inner and outer conduits. The system of the present inventioncomprises suitable closure means which seals the annulus at a secondregion thereof above the location of the packer. This closure meansfunctions with the packer to form a fluidtight compartment within theannulus between the packer and the closure means. In addition, the wellis provided with means forming a confined passageway within thefluidtight compartment. This passageway extends into the compartmentfrom the exterior thereof downwardly through the compartment to alowermost elevation therein and thence upwardly to a level above thislowermost elevation. At this level, the confined passageway opens intofluid communication with the fluidtight compartment. With this systeminstalled in the well, liquids ofditferent densities can be utilized toimpose a pressure on the upper side of the packer sufficient to offsetthe relatively high pressures which may be present in the well below thepacker.

In accordance with a further aspect of the invention, there is provideda method in which the above-described system may be utilized to impose adesired pressure on the upper side of the packer. In this aspect of theinvention, a liquid, commonly termed a packer liquid, is introduced intothe fluidtight compartment within the annulus and a second liquid isintroduced into the confined passageway contained within the fluidtightcompartment. This second liquid is of a density greater than the packerliquid. By so employing these liquids of different densities, thehydrostatic pressure exerted upon the upper side of the packer isincreased by a value equivalent to the differential hydrostatic headimposed by the more dense liquid contained within the confinedpassageway.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical section ofawellbore containing an inactivated manometer-type fluid piston in thesealed annulus between a tubing and wellbore casing; and

FIG. 2 is the same vertical section as FIG. 1 with the exception thatpacker liquid is present in the annulus and the manometer-type fluidpiston is activated to impose a predetermined pressure on the upper sideof the packer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, thereis illustrated a well equipped with inner and outer conduits and apacker sealing the annulus between the conduits in accordance withconventional practice. The well is further equipped with a preferredembodiment of the present invention whereby a pressure greater than thatnormally associated with the hydrostatic head of packer liquid withinthe annulus may be imposed upon the packer.

More particularly, and as shown in FIG. 1, a wellbore 1 penetrates theearths surface 3, upper crust 5, and a subterranean formation 7.Formation 7 may be a productive formation such as an oil and/or gasreservoir in which the innate formation fluids are at a relatively highpressure. The well is provided with an outer conduitwhich takes the formof a casing 9 which is cemented within the well by a cement sheath 11.The well also includes a production tubing 13 which is located withinthe casing 9. The production tubing extends from a location adjacent theformation 7 to the surface of the earth and provides a passageway forthe production of fluids from the well. The well is equipped with apacker 19 which seals off the upper portion of the well annulus from thelower portion of the well which is open to the flow of fluids fromformation 7. Packer 19 typically will be set immediately above formation7 as illustrated in the drawing.

In accordance with the present invention, there is provided a closuremember 17, e.g. a casinghead, which seals the annulus between the casing9 and the tubing 13 at an upper location. The closure member 17 and thepacker 19 cooperate to form a fluidtight compartment 21 within theannulus between the closure member and the packer. The well alsoincludes a manometer-type structure 15 which provides a confinedpassageway within the fluidtight compartment 21. Structure 15 iscomprised of an outer tubular member 16 and an inner tubular member 14.Tubular member 14 extends to the exterior of the fluidtight compartment21 through the closure member 17. Outer member 16 is provided with anopening 12 above the bottom thereof. As can be seen from an examinationof FIG. 1, tubular members 14 and 16 provide a confined passageway 1511which extends into compartment 21 and downwardly therethrough to alowermost elevation defined by the bottom of tubular member 16. Theannulus between the inner and outer tubes 14 and 16, respectively,provides a continuation of this passageway back upwardly throughcompartment 21 to the opening 12. This opening provides for fluidcommunication between the confined passageway and the compartment 21 ata level above the bottom of the confined passageway.

The concentric arrangement of tubular members illustrated is thepreferred structure for forming the confined passageway withincompartment 21. This arrangement can be easily installed and withdrawnfrom the well and fits readily within the annular space between thecasing 9 and tubing 13. However, it will be recognized that the confinedpassageway may be formed by other suitable structures. For example, theconfined passageway may be formed by a U-shaped tubular member whichextends downwardly through compartment 21 and then upwardly a relativelyshort distance from the bottom thereof.

In utilizing the system shown in FIG. 1 to impose a desired pressure onthe upper surface of packer 19, a packer liquid 22 is introduced intocompartment 21 and a second liquid, of a density greater than that ofthe packer liquid, is introduced into the confined passageway 15a.Preferably this second liquid has a density of at least twice thatof thepacker liquid. The greater the density of this second liquid, thesmaller the amount needed to increase the pressure on the wellhead sideof packer 19 by a given value. The two liquids preferably are immisciblewith one another to restrict mixing. Bromoform,

7 other. halogenated hydrocarbons, and mercury are examples of denseliquids which may be used as the second liquid in the fluid piston.Compartment 2] is filled'with a corrosion inhibited packer liquid viainlet opening 23a located adjacent the upper end thereof. As shown inFIG. 1, opening 230 is provided with a conduit 23, valve 25, and pump27. During the filling process, air is evacuated from compartment 21 viaa gas outlet 29a through closure means 17. Gas outlet 29a is providedwith a valve 31 and conduit 29. Valve 31 is normally opened to removeall air and gas from compartment 21. This allows compartment 21 to becompletely filled with packer liquid. A sufficient amount of a secondliquid having a density greater than the packer liquid is injected intofluid piston via tubular member 14 to increase the pressure on the upperside of packer 19 to an amount which approximately equals the pressureon the formation side of packer 19. The second liquid injected into thefluid piston settles to the bottom thereof. In FIG. 1, compartment 21 iscompletely filled with a corrosion inhibited packer liquid and fluidpiston 15 has a dense liquid filling the bottom thereof. In this state,the pressure exerted on the upper side of packer 19 is imposed solely bythe hydrostatic pressure of the packer liquid filling compartment 21.

As additional second liquid is put into fluid piston 15 via tubularmember 14, the pressure exerted on the upper side of packer 19 isincreased and the configuration approaches that of FIG. 2. Asillustrated by HQ 2, the packer liquid completely fills compartment 21including tubular member 16 above interface 18 between the relativelydense liquid and packer liquid 22. As further second liquid is put intotubular member 14 of fluid piston 15, the difference in height betweenthe second liquid in tubular member 14 and tubular member 16 isincreased since the packer liquid and second liquid are immiscible onewith the other and both are essentially incompressible. The pressure onthe upper side of packer 19 is thus increased by an amount correspondingto the difference in hydrostatic pressure produced by the second liquidin tubular members 14 and 16.

In a further preferred structure of this invention, the inner tubularmember 14 is flared to form a reservoir 14a of increased volume. Thepurpose of flaring this inner tubular member is best understood by thefollowing description in reference to FIG. 2. Under the conditions ofFIG. 2, the packer liquid in the fluidtight compartment is pressurizedby the manometer-type fluid piston. Since both the packer liquid and thefluid piston liquid are essentially incompressible, any small leak ofliquid from the fluidtight compartment would produce a large decrease inpressure. However, the flared portion of the inner tube of themanometer-type fluid piston serves as a reservoir of fluid pistonliquid. Thus, in the case of a small leak there is less of a decrease inthe height of the dense liquid in the inner tube and less pressuredecrease than there would be if it were not for the flared portion whichserves as a reservoir.

It is desirable to impose a pressure on the upper side of packer 19which is essentially equal in value to the pressure existing on thelower side of packer 19, imposed by formation 7. The pressure imposed onthe upper side of packer 19 is made up of two components, (1) thehydrostatic pressure of the packer liquid in compartment 21, and (2)hydrostatic pressure imposed at the casinghead by manometer-type fluidpiston 15. This relationship where the pressure on'the upper side ofpacker 19 is equal to the pressure on the lower side of packer 19 isrepresented by the following equation:

P +P =P,. l where: P hydrostatic pressure imposed by the column ofpacker liquid filling compartment 21,

P hydrostatic pressure at the casinghead imposed by the manometer-typefluid piston, and

P pressure imposed on the lower side of packer 19 by formation 7, Thus,P =P,--P,.. (2)P,- is determined by measuring with conventional meansthe pressure on the lower side of packer 19. P is determined bymultiplying the height of the column of packer liquid in compartment 21by the pressure gradient (related to density) of the packer liquidfilling compartment 21. Thus P to be imposed by the fluid piston 15 isdetermined by subtracting Pp from P A sufficient amount of second liquidis then added to tubular member 14 of fluid piston 15 to impose an addedpressure of P at the casinghead 17.

Remembering that P =P,--P p and that F is known and P can be determined,the desired P can be obtained. For example, where P,=7,650 p.s.i. and P=10,000 (0.45 p.s.i./ft.= 4,500 p.s.i., then P desired P[" Pp=7,6504,500=3,l50 p.s.i. Thus, dense liquid is added into tubular member 14until a P at the casinghead of 3,150 p.s.i. is measured. This results ina configuration such as seen in FIG. 2 where the length of the column ofdense liquid in the first passageway comprising tubular member 14 is9,000 feet and the length of the column of the dense liquid in thesecond passageway comprising tubular member 16 is 1,000 feet and thelocation of interface 18 is 1,000 feet above the top of packer 19. Thespecific gravity of the corrosion inhibited packer liquid is slightlygreater than 1, giving a pressure gradient of 0.45 p.s.i. per foot. Thespecific gravity of the dense liquid in the manometer-type fluid pistonis exactly twice that of the packer liquid, giving a pressure gradientof0.90 p.s.i. per foot. Thus the pressure exerted at interface 18 isequal to (9,000 feet 1,000 feet) times 0.90 p.s.i./ft. or 7,200 p.s.i.The pressure at the casinghead is equal to 7,200 p.s.i. minus thehydrostatic pressure exerted by the packer fluid in compartment 21 aboveinterface 18 or 7,200-(9,000X0.45 )=3,l50 p.s.i. the desired PTherefore, a condition of pressure balance across packer 19 is obtained.

What 1 claim is:

. 1. In a well having inner and outer conduits therein defining anannulus and having a packer in said annulus at a first region of saidwell, a system adapted for the application of pressure on the upper sideof said packer comprising:

closure means for sealing said annulus at a second region above saidfirst region whereby a fluidtight compartment is formed within saidannulus between said packer and said closure means; and

tubular means forming a confined passageway, said tubular meansextending into said compartment from the exterior thereof between andnonconcentric with said inner and outer conduits, downwardlytherethrough to a lowermost elevation, and thence upwardly to a levelabove said lowermost elevation where said tubular means opens into fluidcommunication with said compartment.

2. The combination of claim 1 further comprising an inlet opening intosaid fluidtight compartment adjacent the upper end thereof wherebyliquid may be introduced into said compartment independently ofsaidconfined passageway.

3. The combination of claim 1 further comprising; a gas outlet openingfrom said compartment through said closure means whereby gas may beevacuated from said compartment concomitantly with the introduction ofliquid thereinto.

4. A system for applying pressure on the upper side of a packer set at afirst region in a wellbore to seal the annulus formed between inner andouter conduits, comprising:

means for sealing the upper end of said outer conduit to form afluidtight compartment of said annulus, said fluidtight compartmentbeing filled with packer liquid; and

means positioned in said annulus to form a manometer-type fluid piston,said last mentioned means having a first tubular member and a secondtubular member concentric one with the other, said first tubular memberbeing of smaller size than said second tubular member, said firsttubular member having fluid communication at its lower end with saidsecond tubular member and said second tubular member having fluidcommunication with said fluidtight compartment above the lower end ofsaid first tubular member, said manometer-type fluid piston beingcharged with a fluid piston liquid having a density greater than thatofsaid packer liquid.

5. The system of claim 4 wherein the upper portion of said first tubularmember is flared to form a reservoir of increased volume.

6. In a well having inner and outer conduits therein defining an annulusand having a packer in said annulus at a first region of said well and aclosure sealing said annulus at a second region above said first regionwhereby a fluidtight compartment is formed within said annulus, a methodfor applying pressure on the upper side of said packer comprising:

introducing a packer liquid into said fluidtight compartment within saidannulus; and

introducing a second liquid having a density greater than said packerliquid into a confined passageway within said compartment, said confinedpassageway extending into said fluidtight compartment from the exteriorthereof, downwardly therethrough to a lowermost elevation, and thenceupwardly to a level above said lowermost elevation where said confinedpassageway opens into fluid communication with said fluidtightcompartment.

7. The method of claim 6 wherein said second liquid has a specificgravity of at least twice that of said packer liquid.

8. The method of claim 6 wherein said second liquid is immiscible withsaid packer liquid.

9. in a well having inner and outer conduits therein defining an annulusand having a packer in said annulus at a first region of said well, asystem adapted for the application of pressure on the upper side of saidpacker comprising:

closure means for sealing said annulus at a second region above saidfirst region whereby a fluidtight compartment is formed within saidannulus between said packer and said closure means, said fluidtightcompartment containing packer liquid therein; and

means forming a confined passageway which extends into said compartmentfrom the exterior thereof, downwardly therethrough to a lowermostelevation, and thence upwardly to a level above said lowermost elevationwhere said passageway opens into fluid communication with saidcompartment, said confined passageway containing a second liquid ofgreater density than said packer liquid.

10. The combination of claim 9 wherein said second liquid has a specificgravity of at least twice that of said packer liquid.

1. In a well having inner and outer conduits therein defining an annulusand having a packer in said annulus at a first region of said well, asystem adaptEd for the application of pressure on the upper side of saidpacker comprising: closure means for sealing said annulus at a secondregion above said first region whereby a fluidtight compartment isformed within said annulus between said packer and said closure means;and tubular means forming a confined passageway, said tubular meansextending into said compartment from the exterior thereof between andnonconcentric with said inner and outer conduits, downwardlytherethrough to a lowermost elevation, and thence upwardly to a levelabove said lowermost elevation where said tubular means opens into fluidcommunication with said compartment.
 2. The combination of claim 1further comprising an inlet opening into said fluidtight compartmentadjacent the upper end thereof whereby liquid may be introduced intosaid compartment independently of said confined passageway.
 3. Thecombination of claim 1 further comprising; a gas outlet opening fromsaid compartment through said closure means whereby gas may be evacuatedfrom said compartment concomitantly with the introduction of liquidthereinto.
 4. A system for applying pressure on the upper side of apacker set at a first region in a wellbore to seal the annulus formedbetween inner and outer conduits, comprising: means for sealing theupper end of said outer conduit to form a fluidtight compartment of saidannulus, said fluidtight compartment being filled with packer liquid;and means positioned in said annulus to form a manometer-type fluidpiston, said last mentioned means having a first tubular member and asecond tubular member concentric one with the other, said first tubularmember being of smaller size than said second tubular member, said firsttubular member having fluid communication at its lower end with saidsecond tubular member and said second tubular member having fluidcommunication with said fluidtight compartment above the lower end ofsaid first tubular member, said manometer-type fluid piston beingcharged with a fluid piston liquid having a density greater than that ofsaid packer liquid.
 5. The system of claim 4 wherein the upper portionof said first tubular member is flared to form a reservoir of increasedvolume.
 6. In a well having inner and outer conduits therein defining anannulus and having a packer in said annulus at a first region of saidwell and a closure sealing said annulus at a second region above saidfirst region whereby a fluidtight compartment is formed within saidannulus, a method for applying pressure on the upper side of said packercomprising: introducing a packer liquid into said fluidtight compartmentwithin said annulus; and introducing a second liquid having a densitygreater than said packer liquid into a confined passageway within saidcompartment, said confined passageway extending into said fluidtightcompartment from the exterior thereof, downwardly therethrough to alowermost elevation, and thence upwardly to a level above said lowermostelevation where said confined passageway opens into fluid communicationwith said fluidtight compartment.
 7. The method of claim 6 wherein saidsecond liquid has a specific gravity of at least twice that of saidpacker liquid.
 8. The method of claim 6 wherein said second liquid isimmiscible with said packer liquid.
 9. In a well having inner and outerconduits therein defining an annulus and having a packer in said annulusat a first region of said well, a system adapted for the application ofpressure on the upper side of said packer comprising: closure means forsealing said annulus at a second region above said first region wherebya fluidtight compartment is formed within said annulus between saidpacker and said closure means, said fluidtight compartment containingpacker liquid therein; and means forming a confined passageway whichextends into said compartment from the exterior thereof, downwardlytherethrough to a lowermost elevation, and thence upwardLy to a levelabove said lowermost elevation where said passageway opens into fluidcommunication with said compartment, said confined passageway containinga second liquid of greater density than said packer liquid.
 10. Thecombination of claim 9 wherein said second liquid has a specific gravityof at least twice that of said packer liquid.